Microbio 10

the killing or removal of all viable organisms (including endospore)

Effectively limiting microbial growth

The treatment of an object to make it safe to handle

Directly targets the removal of all pathogens, not necessarily all microorganisms

Heat, Radiation, Filter

• Used on external surfaces: sterilants, disinfectants, sanitizers, antiseptics
• Used internally: antibiotics, anivirals, antifungals

Heat

High temperatures denature macromolecules

Amount of time required to reduce viability tenfold is called the decimal reductio time (D)

Thermal death time is the time needed to jill all cells at a given temperature

Thermal death time is dependent on the population size of the microorganism tested. Need to standardize the starting number of ells to be able to compare the sensitivity of different microorganisms

• The autoclave is a sealed device that uses stame under pressure:
• Allows temperature of water to get above 100°C
• At 15psi, steam reach 121°C, sterilization is achieved in 10-15 min
• The object being sterilized wil reach this temperature. Not suitable for heat-sensitive object/liquid
• Not the pressure that kills things, but the high temperatures

• Pasteurization is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
• Does not kill all organisms, it is not a method of sterilization

• Listeriamonocytogenes
• Salmonella enterica
• Campylobacter
• E. Coli O157:H7

72°C for 15 seconds

65°C for 30 mins

• UV has sufficient energy to cause modifications and breaks in DNA, which inhibit replication, transcription and cause microorganism death
• UV is useful for decontamination of surfaces
• Cannot penetrate solid, opaque, or light-absorbing surfaces

• Electromagnetic radiation that produce ions and other reative molecules
• Generates electrons, hydroxyl radicals, and hydride radicals
• Amount of energy required to reduce viability tenfold is analogous to D value

• Cathode ray tubes (electrons)
• X-Rays
• radioactive nuclides

Radiation is used for sterilization in the medical field and food industry

• Filtration avoids the use of heat on sensitive liquids and gases
• Pores of filter are too small for organisms to pass through
• Pores allow liquid or gas to pass through

• Fibrous sheet or mat made from an array of fiber (paper or glass)
• Use to sterilize liquid, air
• HEPA filters

• Function more like a sleve
• A type of membrane filter is the nucleation track (nucleopore) filter
• Filtration speed can be increased by syringe, pump, or vacuum

• Bacteriostatic
• Bacteriocidal
• Bacteriolytic

Inhibit growth of microorganism

Kill microorganism

Kill microorganism by inducing lysis

• The smallest amount of an agend needed to inhibit growth of a microorganism
• Varies with the organism used, inoculum size, temp, pH, etc

The lowest concentration of an agent that kills a test organism

The lowest concentration of an agent that kills a test bacterium

• Antimicrobial agent added to filter paper disc
• MIC is reached at some distance
• Zone of inhibition- area of no growth around disc

Area of no growth around disc

• Products used to control microorganisms in commerical and industrial applications
• Products designed to prevent growht of human pathodens in inanimate environments and on external body surfaces

• Chemicals in foods
• Air-conditioning cooling towers
• Textile and paper products
• Fuel tanks

• Sterilants
• Disinfectants
• Sanitizers
• Antiseptics

• Destroy all forms of microorganism, including endospore
• COLD STERILIZATION

• Applied to nonliving obects or surface (can be toxid for animals/humans)
• Does not kill endospore

• Applied to the surface of living tissues or skin (must not be toxic for anials/humans)
• Does not kill endospore

• Antibiotics, antitifungals, antivirals: applied outside or inside the body of animals/humans (must not be toxic for animals/humans)
• Does not kill endospore

Disinfectant/antiseptic- distrupt cytoplasmic membrane, protein denaturant (high concentration)

Disinfectant/Antiseptic- Lipid solvent and protein denaturants

Disinfectant/Antiseptic/Sterilant- Chlorine (S/D): oxidizing agent- Iodine (A): iodinate tyrosine residues in protein, oxidizing agent

Disinfectant- modify proteins, interact ith RNA, DNA...severalo different mechanism

Interact with phospholipids of cytoplasmic membrane

Disinfectant/Sterilant- Ethylene gas, formaldehyde, glutaraldehyde. Very toxic

• Molecular structure
• Mechanism of action
• Spectrum of antimicrobial activity

• NO side effects, must be far more toxic for bacteria than mammalian cells
• Broad spectrum of activity to faciitate rapid medical intervention
• Appropriate bioavailability and pharmacokinetic (must reach the site of infection)
• Low cost to develop and manufacture

The ability to inhibit or kill a pathogen without affecting the host

One of the first antimicrobial drugs, use to treat syphilis (treponema pallidum)

• Structurally similar to growth factors but do not function in the cell
• Analogs similar to vitamins, amino acids, and other compounds

• Discovered by Gerhard Domagk in the 1930s
• Sulfanilamide is an analogue of p-aminobenzoid acid
• Bacteriostatic

• A growth analog effective only against Mycobacterium
• Interferes wwith synthesis of mycolic acid

• Have been formed by the addition of bromine or fluorine
• Stop DNA replication, translation

Antibacterial compounds that interfere with DNA gyrase

Antibiotics are antimicrobial agents naturally produced by a variety of bacteria and fungi to inhibit or kill other microoranisms

>1%

Antibiotics that are modified to enhance efficacy

The cell wall is a major factor

• One of the most important groups of antibiotics of all time
• Include penicillins, cephalosporins, and cephamycins
• Btericidal, bacteriolytic

• Discovered by Alexander Flemin, isolated from Penicillium chrysogenum (mold)
• Primarily effective against gram-positive bacteria
• Some synthetic forms are effetive against some gram-negatie bacteria
• Inhibit cell wall synthesis

• Produced by funcus Cephalosporium
• Same mode of action as the penicillins
• Commonly used to treat conorrhea (Neisseria gonorrhea)

• Kanamycin, neomycin, amikacin, streptomycin
• Target 30S subunit of ribosome, cause misreading of mRNA
• Bactericidal

• Bind to 23S rRNA and block peptide elongation
• Bacteriostatic

• Ethromycin
• Broad-spectrum antibiotic that targets the 50S subunit of ribosome, block protein synthesis
• Bacteriostatic

• Broad-spectrum inhibition of protein synthesis, bacteriostatic
• Inhibits functioning of 30S ribosomal subunit, block protein synthesis

• Also produced by Streptomyces
• Used to treat gram-positive bacterial infections
• Forms pores in cytoplasmic membrane

• New structural calss of antibiotic
• Broad-spectrum, effective agains MRSA and vacomycin-resistant enterococci

The acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive

• Lack target sites (no peptidoglycan)
• Modify target sites
• Lack of uptake mechanism

• Destroy or modify the antibiotic (beta-lactamase)
• Modify the target site
• Modify uptake mechanism
• Efflux pumps: reduce intracellular concentration

• 1. Mutation of target sites
• 2. Plasmic acquisition

Evidence indicates that R plasmids predate the antibiotic era (antibiotics come from nature)

R plasmids can be transferred between bacteria of the same species or related species

Methicillin-resistant S. Aureus (MRSA)

Resistance can be minimized by using antibiotics correctly and only when needed (reduce selection)

• Most antiviral drugs also target host structures, resutling in toxicity (viruses use host cell machinery)
• Risk to the host may not justify the use of antiviral

NO

Most successful and commonly used antivirals are the nucleoside analgs (eg AZT): block reverse transcriptas and production of viral DNA (RNA viruses)

Inhibit the processing of large viral proteins into individual components

Prevent viruses from successfully fusing with the host cell

Fungi pose special problems for chemotherapy because they are eukaryotic: much of the cellular machinery is the same as that of animals and humans

• Ergosterol synthesis (nystatin, fluconazole)
• Cell wall synthesis (inhibitor of chitin synthesis)